1. Field of the Invention
The present invention relates to a wide-angle photographic lens system having a shortened overall length.
2. Description of the Prior Art
A recent tendency in designing 35 mm-size compact cameras is to provide a camera body with a protective cover which is supported for slidable covering and uncovering movement in order to protect the taking lens. In such cameras, the taking lens, if it has a long lens system, requires the provision of a large-sized protective cover, resulting in a bulky camera body. Therefore, when making a camera body compact, it is first of importance to incorporate a taking lens having a shortened overall length of the lens system thereinto.
As is well known in the art, it is essential for shortening the overall length of a lens system to make the total focal length thereof shorter, i.e., the angle of view larger and to decrease the telephoto ratio thereof as much as possible. It should be noted herein that the telephoto ratio is the value of the overall length of the lens system divided by the total focal length thereof. For the decrease of the telephoto ratio, it is known to comprise the lens system of forward lens means with a positive power and rearward lens means with a negative power. However, such a lens system having a positive-negative power distribution in this order from the object side shows a tendency to increase various aberrations such as distortion, astigmatism and the like with a decrease of the telephoto ratio of the lens system itself or an increase of the angle of view thereof. An example of such a wide-angle lens system having the positive-negative power distribution is disclosed in, for example, Japanese Patent Unexam. Publ. No. 57-116313. The wide-angle lens system shown in the foregoing Jap. Patent Unexam. Publ. No. 57-116316 has an F ratio of 2.8, an angle of view of 59.degree. and a telephoto ratio of 1.0. When incorporating the wide-angle lens into a certain type of 35 mm-size compact camera, the overall length of the lens system will be estimated to be 38 mm which is considered too long.